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<br />00090J <br /> <br />, <br /> <br />and extended stopovers during spring migration are not known. <br />These observations may indicate the Platte River fulfills a <br />biological requirement innate in the migrational ecology of the <br />Aransas-Wood Buffalo population. Alternatively, they may <br />indicate that high flows better fulfill the proximal migrational <br />requirements of roosting, loafing, and feeding habitats, and the <br />predominance of the spring observations is simply because high <br />flows are more common during spring. <br /> <br />Recommended Targets: <br /> <br />Flows in a range from 1300 to 2000 cfs should be protected and <br />improved. Seventeen of 25 recent whooping crane sightings <br />occurred in a range from 1200 to 2290, and both these points mark <br />increased whooping crane use in relation to the relative <br />frequency of flows at that level. <br /> <br />Flows at and below 2000 should not be reduced beyond their <br />present frequency of occurrence. Habitat models indicate the <br />highest roost habitat values from 2000 to 2500. The 2000 cfs <br />level is a point of relatively high habitat value for all models, <br />and all models indicate habitat values decrease rapidly as flows <br />are reduced below this point (the point appears to represent a <br />break in the habitat versus flow curves). A 2000 cfs flow is <br />intermediate to the range of higher flows where many of the <br />whooping crane observations have occurred. It is also near <br />somewhat below the flow levels that occurred during three of four <br />periods of extended use of the river by whooping cranes. currier <br />and Eisel (1984) also concluded that a 2000 cfs provided high <br />whooping crane roost suitability based on wetted width criteria <br />and analysis of aerial photography. <br /> <br />Any additional water that becomes available to improve habitat <br />should first be used to improve the habitat by increasing low <br />flows below 1300 cfs up to 1300 cfs. Further improvements of <br />roost habitat could be made by increasing flows between 1300 and <br />2000. A number of observations have occurred near the 1300 <br />level, and this level appears to correspond with marked <br />improvement in the area of wetted channel. using the habitat <br />model output, 1300 cfs is equivalent to anywhere from 75 percent <br />(Ziewitz and C4R models) to 45 percent (Model C5R) of the best <br />habitat achievable by flow management. The flows needed to <br />restore and maintain wet meadows are an essential and inseparable <br />component of whooping crane migrational habitat and are described <br />elsewhere in this report. <br /> <br />6 <br />